The primary emphasis in genetic modification has been directed to prokaryotes and mammalian cells. For a variety of reasons, plants have proven more intransigent than other eukaryotic cells to genetically manipulate. However, in many instances, it is desirable to effect transcription of an introduced nucleotide sequence of interest in a plant.
Expression of a DNA sequence in a plant is dependent, in part, upon the presence of an operably linked transcriptional control sequence, such as a promoter or enhancer, which is functional within the plant. The transcriptional control sequence determines when and where within the plant the DNA sequence is expressed. For example, where continuous expression is desired throughout the cells of a plant, constitutive promoters are utilised. In contrast, where gene expression in response to a stimulus is desired, an inducible promoter may be used. Where expression in specific tissues or organs is desired, a tissue-specific promoter may be used.
Accordingly, there is a substantial interest in identifying transcriptional control sequences, such as promoters or enhancers, which are active in plants. Frequently, it is also desirable to specifically or preferentially direct transcription in particular plant organs, tissues or cell types, or at particular developmental stages of plant growth. Thus, isolation and characterisation of transcriptional control sequences, which can serve as regulatory regions for the expression of nucleotide sequences of interest in particular cell, tissues or organs of a plant, would be desirable for use in the genetic manipulation of plants.
Reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in any country.